Chemistry Prelim Defense: Application of Auxiliary Field Quantum Monte Carlo to Actinide Thermochemistry

About the event

Title: Application of Auxiliary Field Quantum Monte Carlo to Actinide Thermochemistry

Speaker: Brooke Bonar

Group: Peterson

Abstract: Actinide molecules have been of great interest to chemists, both for their radioactive nature and their rich chemistry. Their applications in the nuclear fuel cycle and in complex waste remediation makes foundational knowledge of actinide thermochemistry vital.  Air-free apparatuses are often necessary for experimental actinide thermochemical work, and these apparatuses are costly and time consuming to install. Computational work provides a viable way to avoid these experimental obstacles. The relativistic Feller-Peterson-Dixon (FPD) methodology has been used to calculate highly accurate (within 1 kcal/mol) thermochemical properties of thorium oxides, uranium oxides, and many other actinide containing molecules. The FPD methodology primarily utilizes coupled cluster with singles, doubles, and perturbative triples (CCSD(T)) which is not suitable for multireference molecules. Many relevant actinide molecules, for instance, PuO3, require multireference wavefunctions to accurately determine their thermochemical properties. Auxiliary Field Quantum Monte Carlo (AFQMC) is an emerging stochastic method, which allows multideterminant wavefunctions and shows promise as a replacement for coupled cluster theory within the FPD methodology.

The purpose of this work is to determine the utility of AFQMC for use within the FPD methodology, primarily in the context of bond dissociation energies (BDEs). Preliminary work includes comparisons of AFQMC energies to coupled cluster theory. This work proposes the determination of BDEs for challenging, multireference transition metal molecules and actinide molecules.